The Seagate Momentus XT Hybrid Drive and the Netbook

October 27, 2012
SSDs (Solid State Drives) are fast but expensive and low in capacity while mechanical drives are slower but inexpensive and offer larger capacities. Is there a way to combine the best of both worlds?

The Seagate Momentus XT 750GB hybrid drive attempts to combine SSD speeds with a large 750GB capacity in the space of a laptop hard drive. Does a hybrid drive offer better performance than a regular drive? And, more importantly, how well does it perform in the Acer Aspire One 722 netbook running Ubuntu 10.10 64-bit?

About the Drive

My drive arrived brand new in Western Digital packaging. Talk about recycling…

The Seagate Momentus XT 750GB 7200 RPM Hybrid drive shipped in Western Digital packaging.

The dimensions are the same as any other standard 2.5″ laptop drive, and the height is about 9mm. So, the Momentus XT is too tall for the Acer Aspire One 756 netbook. The standard SATA interface is fine, but the 756 requires laptop drives that are 5mm in height or else the back panel will not slide back into place.


The idea behind a hybrid drive is to cache the frequently used data from the slower drive platters into solid state memory so the data will be available for faster access the next time the system boots. This is different from a hard drive’s cache memory. Cache memory is deleted when the computer or netbook is turned off, but SSD memory remains when the computer is turned off. This way, the drive can access the data that was last used faster from the SSD memory instead of grabbing it from the slower platters.

“So, what does that translate to in real life?”

In theory, we should see faster system boots, faster system shutdowns, and faster program and data access for the most commonly accessed programs and data. For accessing data already in the SSD memory, the hybrid drive should perform as fast as a true SSD.

Does It Work?

Yes. Immediately, this drive made a noticeable difference in the 722’s performance. Compared to a regular 750 GB non-SSD Seagate drive, the netbook’s boot times were faster, shutdown times were faster, and opening programs took less time.

Of course, this happened after the second or third reboot because the data much be cached into the SSD memory first. However, after using this drive for quite some time, it is beyond a doubt, much faster than a regular 7200 RPM laptop drive.

My 722 netbook running Ubuntu 10.10 already felt fast and snappy, but this drive added a little extra boost
in performance to make the netbook feel slightly faster.

Real Facts

Keep things in perspective. The Momentus XT is not going to produce eye-catching, blazing-fast results. The netbook’s drive interface is nowhere near as fast as a desktop system, so no matter what kind of hard drive is installed–SSD or not–the drive will be limited by the I/O bottleneck.

Even a true SSD tends to be slower on a netbook than on a desktop system. I have used three kinds of drives with the 722 netbook: regular laptop drives, true SSDs, and this hybrid drive. For data already cached in the hybrid’s SSD memory, the Momentus XT performs just as fast as a true SSD, but for accessing non-cached data, the drive is as fast a normal 7200 RPM laptop hard drive. Even then, the 7200 Momentus XT is faster than a 5400 RPM laptop drive.

Another important point to note is that the actual usable space of the hard drive after formatting will be less than 750GB. Usually, it will be about 7% less than the quoted capacity, so this 750 GB drive formats to about 698 GB for ext3, ext4, and NTFS. (ext3 and ext4 will need to have their reserved blocks set to 0 in order to maximize the available space after formatting.) This is true for any hard drive.

Noise Level

The Momentus XT contains mechanical parts, so the spin noise is audible from inside the netbook. It is nothing terribly noisy or annoying, but the familiar “swishing” sound can be heard at close ranges. However, it is more quiet than expected. I have heard 5400 RPM drives louder than this, and the netbook’s CPU fan is actually louder. So, hard drive spin noise is really not an issue.


Rather than performing tedious benchmarks, I was more interested in timing a few real-life operations with a standard stopwatch. Is the Momentus XT hybrid drive really faster? If so, how much?

Comparisons are made by performing the same tests on an Acer Aspire One 722 netbook running Ubuntu 10.10 64-bit with kernel 3.4.0. One drive is a standard 750GB 7200 RPM laptop drive, and the other is the Momentus XT 7200 RPM hybrid drive.

Drive Type            PowerOn to Login   Login to Usable Desktop    Total    Shutdown
Standard 7200RPM      45s                26s                        1m11s    5s
Momentus XT Hybrid    28s                13s                          41s    3s

Programs can vary, so their cold startup times tend to vary. For example, Firefox sometimes take 5 seconds to open on a standard drive, but it sometimes opens in 3 seconds or less on the hybrid drive (from a cold boot if Firefox was opened during the previous session). This is why no specific program times are given. They vary too much to produce reliably consistent timings. The SSD memory is limited, so its data will be overwritten with more frequent data. If data is not cached, then the drive must retrieve it from the platters, and in this way, the hybrid drive is no different from any other 7200 RPM drive.

However, after extended use over a large variety of software and system daemons, the hybrid drive is, in general, consistently faster than a standard drive, and there is certainly a noticeable speed improvement, even if it might be a slight one. People tend to have specific computer-usage habits and open a small set of programs most of the time. A hybrid drive is well-suited for this kind of computer usage, and this was true during my usage.


The Seagate Momentus XT hybrid drive is one of those products where I can immediately see an improvement in system performance. It might not be as fast as a true SSD all of the time, but most of the time, it outperforms a regular drive and comes pretty close to matching a true SSD. Plus, it has 750 GB of unformatted storage space, which is far more than any SSD can provide at an affordable price.

Startup and shutdown times are definitely faster by about half the time in most cases, and frequently used programs, data, and OS menus and windows pop up quicker. The speed increase tends to be more on the “slight improvement” side rather than the “Wow! That’s smoking fast!” side, but those awe-inspiring moments can happen. The performance is noticeable, pleasing, welcome, and makes this a worthwhile purchase.

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